Method for preparing silica compositions, silica compositions and uses thereof

Abstract

A method for producing a flowing silica composition including a sol-gel transfer, where redispersion is carried out. The redispersion includes adding, after having reached gel point of the sol-gel transfer, liquid into the gel formed by the sol-gel transfer, and the addition being made within a sufficiently short time period after reaching the gel point, to result, after mixing of the gel and the liquid, in a rheologically homogenous flowing silica composition, which is and remains injectable as such, or by short stirring <30 s, through a thin 22 G needle. Also disclosed are flowing silica compositions and gels obtainable by methods of the invention, and uses of flowing silica compositions.

1 . A method of producing a flowing silica composition, wherein said method comprises a sol-gel transfer and wherein redispersion;
 comprising adding, after having reached gel point of said sol-gel transfer, liquid, preferably water and/or alcohol, into the gel formed by said sol-gel transfer, and said adding being made within a sufficiently short time period after reaching said gel point, said time period depending on temperature and the recipe of the sol-gel transfer, to result, after mixing to follow of said gel and said liquid, in a rheologically homogenous said flowing silica composition, which is and remains injectable as such, or by short stirring <30 s, through a thin 22 G needle, i.e. a 400 μl aliquot of the sample can at RT be injected with a 1.0 ml syringe, using standard injection procedures, i.e. with one steady pressing of the syringe plunger, without the use of undue force and without phase separation or blockage of the needles occurring during the injection;   
     is carried out. 
   
   
       2 . The method according to  claim 1  characterized in that at least one functional agent, preferably biologically active agent, other than the silica as such, is incorporated into said flowing silica composition, by mixing, preferably before the gel point of the sol-gel transfer. 
   
   
       3 . The method according to  claim 1  characterized in that said flowing silica composition is and remains injectable as such or by stirring <30 s through a 24 G, preferably through a 26 G, more preferably a 28 G and most preferably a 30 G needle. 
   
   
       4 . The method according to  claim 1 , characterized in that adding of the liquid and mixing is carried out within ≦10 d, preferably within ≦1 d, more preferably ≦10 h, even more preferably ≦3 h and most preferably ≦1 h after having reached gel point of the sol-gel transfer. 
   
   
       5 . The method according to  claim 4  characterized in that adding of the liquid and mixing is carried out within ≦20 min, preferably ≦10 min, more preferably ≦5 min and most preferably ≦2.5 min after having reached gel point of the sol-gel transfer. 
   
   
       6 . The method according to  claim 1  comprising the steps of
 a) preparing a sol from at least one liquid, preferably water and/or alcohol, and from silica precursors, preferably alkoxides or inorganic silicate solutions, by hydrolysis and condensation of said silica precursors with subsequent particle formation;   b) optionally adding a functional agent, preferably a biologically active agent or agents, with or without one or more protective agents for said functional agent or agents;   c) letting the sol-gel transfer reach the gel point; and   d) adding, after having reached gel point of said sol-gel transfer, liquid, preferably water and/or alcohol, into the gel formed by said sol-gel transfer, and said adding being made within a sufficiently short time period after reaching said gel point, said time period depending on temperature and the recipe of the sol-gel transfer, to result, after mixing to follow of said gel and said liquid, in a rheologically homogenous said flowing silica composition, which is and remains injectable as such, or by short stirring <30 s, through a thin 22 G needle.   
   
   
       7 . The method according to  claim 6  characterized in that in step a) the sol is prepared from water, an alkoxide or inorganic silicate solution and optionally a lower alcohol, i.e. an alcohol with ≦4 carbons, using an acid or a base as a catalyst, preferably a mineral acid. 
   
   
       8 . The method according to  claim 1  characterized in that said flowing silica composition stored appropriately remains injectable for at least week, preferably 1 month, more preferably 1 year and most preferably 5 years, and said storing preferably comprising storing at ≦37° C., more preferably at ≦25° C., even more preferably at ≦15° C. and most preferably at ≦5° C. 
   
   
       9 . The method according to  claim 1  characterized in that after redispersion regelling of the flowing silica composition is induced. 
   
   
       10 . The method according to  claim 9  characterized in that regelling is induced by adding an agent inducing regelling, preferably selected from the group consisting of a salt, a sol, and a liquid. 
   
   
       11 . The method according to  claim 9  characterized in that regelling is induced by adjusting pH. 
   
   
       12 . The method according to  claim 9  characterized in that regelling of the silica composition as such or as a component of a mixture is induced by carrying out dip, spin, or drain coating; freeze drying; spray drying; fibre spinning; or casting. 
   
   
       13 . A flowing silica composition obtainable by the method of  claim 1 . 
   
   
       14 . The flowing silica composition according to  claim 13  characterized in that at least one functional agent, preferably a biologically active agent, other than the silica gel itself, is incorporated into said flowing silica composition, by mixing, preferably before the gel point of the sol-gel transfer. 
   
   
       15 . The flowing silica composition of  claim 13  characterized in that the flowing silica composition is shear thinning. 
   
   
       16 . A silica gel obtainable by the method of  claim 9 , preferably as particles, fibres, a coating, or formed monoliths. 
   
   
       17 . Use of a flowing silica composition,
 a) optionally comprising one or more functional agents, preferably biologically active agent, other than the silica itself, incorporated into said flowing silica composition; and   b) obtainable by a method comprising a sol-gel process wherein redispersion;
 comprising adding, after having reached gel point of said sol-gel transfer, liquid, preferably water and/or alcohol, into the gel formed by said sol-gel transfer, and said adding being made within a sufficiently short time period after reaching said gel point, said time period depending on temperature and the recipe of the sol-gel transfer, to result, after mixing to follow of said gel and said liquid, in a rheologically homogenous said flowing silica composition, which is and remains injectable as such, or by short stirring <30 s, through a thin 22 G needle, i.e. a 400 μl aliquot of the sample can at RT be injected with a 1.0 ml syringe, using standard injection procedures, i.e. with one steady pressing of the syringe plunger, without the use of undue force and without phase separation or blockage of the needles occurring during the injection; 
   is carried out;   for administering of said silica composition as such and/or said optional one or more incorporated functional agents, preferably biologically active agents, to a human or animal body.   
   
   
       18 . The use according to  claim 17  characterized in that at least one functional agent, preferably biologically active agent, other than the silica as such, is incorporated into said silica composition by mixing, preferably before the gel point of the sol-gel transfer. 
   
   
       19 . The use according to  claim 17  characterized in that said use comprises administering selected from the group consisting of oral, buccal, rectal, parenteral, pulmonary, nasal, ocular, intrauterine, vaginal, urethral, topical, dermal, transdermal and surgically implantable administering. 
   
   
       20 . The use according to  claim 19  characterized in that said use comprises administering by injection. 
   
   
       21 . The use according to  claim 20  characterized in that regelling of the flowing silica composition is induced in combination with the injecting of the flowing silica composition resulting in regelling of the flowing silica composition following the injection. 
   
   
       22 . The use according to  claim 21  characterized in that induction of regelling is carried out prior to injecting the flowing silica composition. 
   
   
       23 . Use of a flowing silica composition, with at least one functional agent, preferably biologically active agent, other than the silica as such, incorporated into said silica composition, wherein redispersion;
 comprising adding, after having reached gel point of said sol-gel transfer, liquid, preferably water and/or alcohol, into the gel formed by said sol-gel transfer, and said adding being made within a sufficiently short time period after reaching said gel point, said time period depending on temperature and the recipe of the sol-gel transfer, to result, after mixing to follow of said gel and said liquid, in a rheologically homogenous said flowing silica composition, which is and remains injectable as such, or by short stirring <30 s, through a thin 22 G needle, i.e. a 400 μl aliquot of the sample can at RT be injected with a 1.0 ml syringe, using standard injection procedures, i.e. with one steady pressing of the syringe plunger, without the use of undue force and without phase separation or blockage of the needles occurring during the injection;   is carried out;   for preservation of the functionality of said at least one functional agent.   
   
   
       24 . Use of a flowing silica composition,
 a) with at least one functional agent, preferably biologically active agent, other than the silica as such, incorporated into the said silica composition, and   b) obtainable by a method comprising a sol-gel transfer wherein redispersion;   comprising adding, after having reached gel point of said sol-gel transfer, liquid, preferably water and/or alcohol, into the gel formed by said sol-gel transfer, and said adding being made within a sufficiently short time period after reaching said gel point, said time period depending on temperature and the recipe of the sol-gel transfer, to result, after mixing to follow of said gel and said liquid, in a rheologically homogenous said flowing silica composition, which is and remains injectable as such, or by short stirring <30 s, through a thin 22 G needle, i.e. a 400 μl aliquot of the sample can at RT be injected with a 1.0 ml syringe, using standard injection procedures, i.e. with one steady pressing of the syringe plunger, without the use of undue force and without phase separation or blockage of the needles occurring during the injection;   is carried out;   for controlled release of said at least one functional agent.   
   
   
       25 . Use of a flowing silica composition,
 a) with at least one functional agent, preferably biologically active agent, other than the silica as such, incorporated into the said silica composition, and   b) obtainable by a method comprising a sol-gel transfer wherein redispersion;
 comprising adding, after having reached gel point of said sol-gel transfer, liquid, preferably water and/or alcohol, into the gel formed by said sol-gel transfer, and said adding being made within a sufficiently short time period after reaching said gel point, said time period depending on temperature and the recipe of the sol-gel transfer, to result, after mixing to follow of said gel and said liquid, in a rheologically homogenous said flowing silica composition, which is and remains injectable as such, or by short stirring <30 s, through a thin 22 G needle, i.e. a 400 μl aliquot of the sample can at RT be injected with a 1.0 ml syringe, using standard injection procedures, i.e. with one steady pressing of the syringe plunger, without the use of undue force and without phase separation or blockage of the needles occurring during the injection; 
   is carried out;   for administering a functional agent or agents for agricultural applications, applications of food production, applications of forestry, pest control and/or environmental applications.